"点石成金?"--碳结构超高压物理力学

文章介绍了石墨和碳纳米管在超高压和／或纳米压痕下的层间sp^2-sp^3键转化、软硬相转换、纳米硬度等研究进展．通过量子力学和分子动力学建模分析研究，发现超高压下石墨和碳纳米管存在软相向硬相转变的双相机制，给出了超高压获取石墨和碳纳米管超硬相的条件．理论计算与实验结果吻合很好，并能合理地解释有关石墨和碳纳米管超高压实验中看似矛盾的各种实验现象．提出了碳结构超高压物理力学概念，可为超高压碳相关物质相变、物化性质调控提供理论方法．     

超高压水射流冲蚀切割岩石断口微观断裂机理实验研究

 由于岩石破碎过程的复杂性，目前对水射流的破岩机理的认识仍然不十分清楚。先采用超高压万能水射流切割机冲蚀切割岩石，然后用扫描电镜对水射流切割岩石断口形貌进行观测，分析了岩石在超高压水射流作用下的破坏形式。观测分析表明，超高压射流切割岩石形成的切槽主要有长形规则和漏斗状两种形状。岩石在水射流作用下的破坏机制主要有拉伸破坏和剪切破坏两种，剥落岩块以穿晶断裂为主，其微观断裂机制是脆性拉伸破坏；切槽凹侧面主要是剪切错动，其微观破坏机制是剪脆性破坏。实验为水射流破岩机理分析提供了实测依据。     

固体氢的压缩行为

 同时考虑分子的平动与转动自由度，用等温等压系综的路径积分蒙特卡罗方法研究了固体氢的状态方程。在有实验数据的区域，计算结果同实验结果符合很好，在无实验数据的超高压区域，计算结果同实验的外推结果符合。为了定量研究零点运动，还计算了体系的能量。     

鲍鱼超高压脱壳工艺的优化及品质研究

实验研究了皱纹盘鲍的超高压脱壳工艺,评价了超高压脱壳对鲍鱼品质的影响。结果表明:超高压处理有利于鲍鱼的脱壳,200MPa保压1min和300MPa不保压的超高压处理组与对照组(手工脱壳)相比,脱壳时间分别节约69%和72%,同时提高了鲍鱼的完整性,鲍鱼肉得率分别提高18%和16%;超高压脱壳处理后,鲍鱼菌落总数从2.2×103 cfu/g减少至270~350cfu/g,水分含量显著增大,pH值变化不显著(P0.05);经超高压脱壳后,鲍鱼肉的亮度L*显著增大,而红度a*和黄度b*较对照组降低,有效改善了鲍鱼的色泽;随着处理压强的增大和保压时间的延长,鲍鱼硬度增加,弹性下降。经综合评价,选择处理压强300MPa、保压时间为零作为最佳超高压脱壳工艺参数。     

超高压水射流形成过程中的压力损失研究

 对超高压水射流形成过程中的压力损失进行了理论研究,并且对不同条件下超高压水射流速度的变化规律进行了实验研究,最后确定了不同条件下超高压水射流的初始参数。结果显示,在超高压水射流形成过程中,压力损失主要是在水流从高压管道进入高压喷嘴时由于流道发生断面收缩而造成的,压力损失大约为最终超高压水射流动能密度的49%;随着喷嘴口径的增大,压力损失减小,整个系统的能量利用率越高;随着水射流压力的增大,压力损失增大,但增大的程度会减小。     

应用于大场景光学演示实验的高亮度白光光源制作

采用超高压汞灯为光源灯芯,制作了应用于大场景物理演示实验教学的高亮度白光光源.该光源可以用于牛顿环干涉实验和光栅衍射实验.     

超高压对枯草杆菌胞外蛋白酶的影响

 以枯草杆菌为研究对象,采用Box-Behnken响应曲面设计,研究了超高压处理对枯草杆菌胞外蛋白酶的影响以及菌体致死与胞外酶的关系。结果表明,超高压能显著抑制枯草杆菌胞外蛋白酶的活性,处理过程中压力和温度是酶失活的主要因素,并且两者之间存在交互作用,超高压处理时温度协同有效。利用Design Expert软件建立了胞外蛋白酶超高压钝化模型,决定系数R₂=0.974 7,调整决定系数R_2,adj=0.942 1。方差分析表明,模型显著,可应用于钝化效果分析与预测。实验结果还表明,超高压处理后枯草杆菌的致死率与胞外蛋白酶活的变化相关性达到极显著水平（R=0.933 0）,胞外酶可作为超高压处理对微生物影响的一个评价指标。     

金刚石生长的高压溶剂中碳的输运及其影响

 实验证实，在金刚石生长的高温超高压溶剂中，碳原子通过溶解扩散而输运，并清楚地看到在溶剂中也有对流现象。而宏观的对流现象的存在及其对金刚石生长的影响是不可忽视的。     

超高压光纤压力传感器理论和实验研究

本文提出了一种新型超高压光纤压力传感器.并用一种几何光学计算方法,用来计算该传感器的耦合系数曲线.在此基础上,设计并加工出一种具有新特点的超高压光纤压力传感器.这种传感器的实验研究结果与理论分析一致.     

光谱分辨条纹相机测量高能啁啾脉冲特性

实验演示了光谱分辩条纹相机法测量高能啁啾脉冲特性，该方法不仅可以用于测量纳秒量级的放大啁啾脉冲，还可以实时监测压缩器的调节.通过实验证实百焦耳PW演示平台输出的百焦耳量级的纳秒啁啾脉冲具有可压缩性.     

氢化铒高温高压下的弹性及热力学性质

利用第一性原理平面波赝势密度泛函理论, 并结合准谐德拜模型, 计算了立方萤石结构ErH2在不同温度和压强下的体积、热膨胀系数、体弹模量和等体热容等弹性性质及热力学性质。在温度高于1 100 K的条件下,计算出的等体热容趋近于Dulong-Petit极限。得到了绝对零度、零压强下ErH2的该结构的晶格常数为0.523 2 nm,与实验值0.523 0 nm非常接近。由不同的原胞体积得出了该体系的单点能与原胞体积的关系的数据;从计算出的高压下的弹性常数,根据立方晶系的力学稳定性条件,推断出立方萤石结构ErH2的相变压力约为20 GPa。     

Electrical property and phase transition of CdSe under high pressure

In situ electrical resistivity measurement of CdSe was performed under high pressure and moderate temperature using a diamond anvil cell equipped with a microcircuit. With the pressure increasing, a sharp drop in resistivity of over two orders of magnitude was observed at about 2.6 GPa, it was caused by the transition to the rock-salt CdSe. After that, the resistivity decreased linearly with pressure. However, in different pressure range, the decreasing degree was obviously different. This attributed to the different electron structures. By fitting to the curve of pressure dependence of resistivity in different pressure range, the relationship of the band gap to pressure was given and the metallization pressure was speculated to be in the range of 70-100 GPa. The temperature dependence of resistivity showed that in the experimental temperature and pressure range the resistivity had a positive temperature coefficient.     

Pressure-induced hydrogen-dominant metallic state in aluminum hydride

Two structural transitions in covalent aluminum hydride AlH3 were characterized at high pressure. A metallic phase stable above 100 GPa is found to have a remarkably simple cubic structure with shortest first-neighbor H-H distances ever measured except in H2 molecule. Although the high-pressure phase is predicted to be superconductive, this was not observed experimentally down to 4 K over the pressure range 120-164 GPa. The results indicate that the superconducting behavior may be more complex than anticipated.     

固氖高压物态方程的量子理论计算

 运用Hartree-Fock计算方法和原子团簇理论,研究了高压下面心立方晶体氖中的二体相互作用、三体相互作用对中心原子势能及冷能的贡献。结合零点振动能,计算得到了固氖在4~208 GPa压强范围内的等温物态方程。结果表明,在较高压强区域内,等温压缩线与高压实验数据符合得非常好;在压强超过100 GPa的区域内,计算得到的等温压缩线较目前已有的理论研究结果系统地改善并提高了3%~5%,精确地解释了固氖的高压实验数据。     

In situ complex impedance spectroscopy of mantle minerals measured at 20 GPa and 1400°C

Electrical conductivities of mantle silicate minerals (Mg_0·9Fe_0·1)₂SiO₄ olivine, wadsleyite and ringwoodite were determined at pressures up to 20 GPa and temperatures up to 1400°C using complex impedance spectroscopy in a high pressure multianvil apparatus. All samples were polycrystalline, synthesized in separate high pressure experiments prior to the electrical measurements. Olivine conductivities up to 10 GPa are very close to values determined at ambient pressure under controlled oxygen fugacities in previous studies indicating a very small pressure dependence. The conductivities of wadsleyite at 15 GPa and ringwoodite at 20 GPa are similar, and both about 100 times greater than for olivine. When compared to conductivity models of Earth's mantle, these results suggest that the steep increase in conductivity near the transition zone is mainly due to the olivine to wadsleyite phase transformation at 410 km depth, with only minor changes in conductivity occurring over the wadsleyite to ringwoodite transformation near 520 km depth.     

液氘状态方程实验数据测量

在神光Ⅱ高功率激光装置上建立了液氘状态方程实验研究系统, 在80 min内实现控温范围12–300 K可调、控温精度±0.03 K、机械震动 ≤20 μm的实验控制精度; 通过镀膜窗口质量筛选和靶体清洁工作解决了低温下窗口材料残余反射率高的难题, 获得了信噪比较好的实验图像; 利用神光II第九路输出3ω (351 nm)、3 ns、1000 J的能力, 采用阻抗匹配方法, 配合任意反射面速度干涉仪诊断系统, 在国内首次获得液氘在约60 GPa压力下的冲击绝热线实验数据, 数据与国外同压力区间数据符合较好, 为下阶段约100 GPa压力范围液氘状态方程的实验研究奠定了基础.     

Melting curve of MgO from first-principles simulations

First-principles calculations based on density functional theory, both with the local density approximation (LDA) and with generalized gradient corrections (GGA), have been used to simulate solid and liquid MgO in direct coexistence in the range of pressure 0 < or = p < or = 135 GPa. The calculated LDA zero pressure melting temperature is T(LDA)m = 3110 +/- 50 K, in good agreement with the experimental data. The GGA zero pressure melting temperature T(GGA)m = 2575 +/- 100 K is significantly lower than the LDA one, but the difference between the GGA and the LDA is greatly reduced at high pressure. The LDA zero pressure melting slope is dT/dp approximately 100 K/GPa, which is more than 3 times higher than the currently available experimental one from Zerr and Boehler [Nature (London) 371, 506 (1994)]. At the core mantle boundary pressure of 135 GPa MgO melts at Tm = 8140 +/- 150 K.     

Simultaneous determination of mean pressure and deviatoric stress based on numerical tensor analysis: a case study for polycrystalline x-ray diffraction of gold enclosed in a methanol-ethanol mixture

It is known that the {100} and {111} planes of cubic crystals subjected to uniaxial deviatoric stress conditions have strain responses that are free from the effect of lattice preferred orientation. By utilizing this special character, one can unambiguously and simultaneously determine the mean pressure and deviatoric stress from polycrystalline diffraction data of the cubic sample. Here we introduce a numerical tensor calculation method based on the generalized Hooke's law to simultaneously determine the hydrostatic component of the stress (mean pressure) and deviatoric stress in the sample. The feasibility of this method has been tested by examining the experimental data of the Au pressure marker enclosed in a diamond anvil cell using a pressure medium of methanol-ethanol mixture. The results demonstrated that the magnitude of the deviatoric stress is ～0.07?GPa at the mean pressure of 10.5?GPa, which is consistent with previous results of Au strength under high pressure. Our results also showed that even a small deviatoric stress (～0.07?GPa) could yield a ～0.3?GPa mean pressure error at ～10?GPa.     

高压下碳纳米管的X射线衍射研究

 用同步辐射原位高压能散X射线衍射技术,对碳纳米管进行了结构和物性的研究,压力达50.7 GPa。在室温常压下,碳纳米管的结构和石墨的hcp结构相似,其(002)衍射线的面间距为d₀₀₂=0.340 4 nm,(100)衍射线的面间距为d₁₀₀=0.211 6 nm。从高压X射线衍射实验看到,当压力升到8 GPa以上时,(002)线变宽变弱,碳纳米管部分非晶化。而当压力从10 GPa或20 GPa卸压至零时,(002)线部分恢复。但当压力升高至最高压力50.7 GPa时,碳纳米管完全非晶化,而且这个非晶化相变是不可逆的。用Birch-Murnaghan方程拟合实验数据,得到体弹模量为K₀=(54.3±3.2)GPa（当K′₀=4.0时）。     

33GPa压力以下液氩冲击温度的实验测量

 利用液氮冷靶系统制取液氩样品,以二级氢气炮作为加载工具,驱动飞片对液氩样品进行平面冲击压缩,实验测量了33 GPa冲击压力以下液氩的冲击温度。飞片速度由磁测速系统测量,冲击波速度和冲击温度用光纤耦合高温计系统测量,粒子速度采用阻抗匹配法计算得到。实验测得当冲击压力为33 GPa时,液氩的冲击温度超过10 000 K;而当冲击压力超过30 GPa时,冲击温度的上升趋势与理论计算相比明显变缓,该压力点正好与以前测得的冲击波速度-粒子速度曲线的拐点一致。